1. Field of the Invention
The present invention relates to a new group of plastics based on fatty acids that can be obtained from natural oils and fats.
2. Technology Review
Natural oils and fats serve not only as initial substances for producing a multitude of technically important basic materials; under certain conditions, they can also be used to a substantially increased extent to produce polymers, in particular plastics. At present, the production of polymers from fats and oils is based essentially on three different possibilities.
The first possibility makes use of the, observation that polyunsaturated fats and fatty acids tend to polymerize when heated or exposed to atmospheric oxygen. These properties are of importance, for example, in the production of linoleum and in the curing of lacquers and varnishes (oil paints) as well as of sealing compounds, e.g., glazier's putty. The field of application in this case is naturally limited to oils with a high content of polyunsaturated fatty acids, so-called drying oils such as linseed oil, wood oil or nut oil.
A second possibility is to use oils and fats which, because of their composition, predominantly contain two or more alcohol groups per triglyceride molecule, and to process them with appropriate reactive compounds, e.g. diisocyanates, to give polymeric structures. Suitable substances for such reactions are, for example, castor oil or hydrogenated castor oil, which can be used directly as triglycerides. However, the range of application of this method is also limited by the available oils and fats and, in addition, the direct use of triglycerides normally permits only such polymers to be produced that are cross-linked and therefore cannot be processed thermoplastically.
The third possibility is to break down the fatty acids contained in oils and fats into diactive fatty acid splitting products such as dicarboxylic acids by splitting reactions, e.g. ozonolysis, the reactive groups, for example, carboxylic acid groups, being attached to both ends of the hydrocarbon chains. According to this method, it is possible to produce azelaic acid from oleic acid on an industrial scale. The dicarboxylic acids can then be reacted with diamines to give polyamides or with diols to give polyesters. It is also common practice in the chemical industry to split ricinoleic acid (from castor oil), react one of the splitting products to give 11-amino-undecanoic acid and polycondensate the latter to give nylon R 11 (Rilsan) . Although thermoplastic polymers as well can be produced via these or other diactive fatty acid splitting products, this method also has decisive drawbacks. On the one hand, splitting the fatty acids into diactive products is relatively complicated an(i involves major losses, and on the other hand considerable amounts of various by-products are formed, especially aliphatic monocarboxylic acids, the chain length of which is less interesting from the technical point of view, and the subsequent purifying operations are therefore difficult.
The above examples already show the basic interest of the plastics industry in using natural fats and oils.